Determine the moment of each of the three forces about point b

The external force and couple moment acting on a body can be reduced to an equivalent resultant force and resultant couple moment. When this resultant force and resultant couple moment is both equal to zero then the body is said to be in equilibrium.

The major assumption for applying these equilibrium equations is that the body remains rigid.

To apply these equilibrium equations, we need to know the known and unknown forces that act on the body. When all the supports are removed by replacing them with forces that prevents the translation of body in a given direction that diagram is called free body diagram.

The magnitude of the resultant force is equal to area under the loading diagram.

The resultant has a line of action the passes through the centroid.

Write the equilibrium equations.

Here, the resultant force is and the resultant moment about any arbitrary point is .

Sign Convention for force: Upward and right forces are positive.

Sign Convention for moment: Anti clockwise moment is positive.